Optical surveillance device

ABSTRACT

An optical monitoring means comprises a plurality of pattern fields, which are arranged at one end of the area to be monitored, objectives at the other end of the area to be monitored and which are respectively associated with the pattern fields, reflectors, which deflect the image rays from the objectives onto a image projection surface, a sensor means, onto which the objectives throw an image of the pattern field, and which scans the image and feeds corresponding signals to a signal processing means, which ascertains whether the image received by the sensor means possesses the same optical characteristics as the pattern fields. As an alternative the monitoring means comprises a series of pattern fields is arranged at opposite sides of an area to be monitored, two units, which respectively comprise an objective and a reflector, are arranged at diagonally opposite corners of the area to be monitored, the units are so rotatably arranged that one objective in each case scans the pattern field arranged opposite to it, and that opposite each reflector a sensor means is placed, onto which the objectives throw the image of the pattern field, and which scans the image and feeds corresponding signals to a signal processing means, which ascertains whether the image received by the sensor means possesses the same optical characteristics as the pattern fields.

BACKGROUND OF THE INVENTION

The invention relates to an optical monitoring means.

For monitoring danger areas around machines, security areas, elevatordoors or the safety monitoring of apartments photoelectric detectors andbeam arrays using same have so far been employed. Such beam arrayssuffer from the disadvantage that a plurality of active elements, i. e.light sources and sensors, must be arranged on either side of themonitored area, something which increases the costs of such a beamarray. Furthermore all active elements must be connected together bywiring in order to permit synchronization and signal processing. Theelectronic circuitry necessary for this is also a substantial costfactor.

The German patent publication 38 42 142 C1 discloses a method for theoptical recognition of objects, the means comprising a sensor means, onwhich an objective projects the image of a pattern field, and a signalprocessing means in order to ascertain whether the image received by thesensor means possesses the same optical characteristics as the patternfield. At one end of the monitored area there is therefore a passiveelement, namely the pattern field, whereas the sensor means togetherwith the associated objective is placed at the other end of themonitored area so that no power supply and control lines must be laidfrom the one end of the monitored area to the other end. Furthermore thenumber of active elements is reduced.

SUMMARY OF THE INVENTION

In contradistinction to this the invention has the aim of creating amonitoring means, which may be implemented at a moderate price, thenumber of active elements being reduced with the possibility of ensuringa compact structure.

In order to attain this object the optical monitoring means of theinvention is characterized by a plurality of pattern fields, which arerespectively arranged at one end of the area to be monitored, objectivesat the other end of the area to be monitored and which are respectivelyassociated with the pattern fields, reflectors, which deflect the imagerays from the objectives onto a image projection surface, a sensormeans, onto which the objectives throw an image of the pattern field,and which scans the image and feeds corresponding signals to a signalprocessing means, which ascertains whether the image received by thesensor means possesses the same optical characteristics as the patternfields.

The monitoring means is made up of detectors of the above mention typeand comprises a plurality of superposed detectors. Owing to thisarrangement a monitoring means is created, whose function is comparablewith that of a beam array, several optical detectors being utilized inorder to form the array of the monitoring means. Nevertheless a singlesensor means suffices, which is best a CCD camera, in order to respondto the image on the image projection surface and to supply correspondingsignals to the signal processing means.

Moreover the invention relates to a monitoring means comprising opticaldetectors of the type initially mentioned, which is characterized inthat a series of pattern fields is arranged at opposite sides of an areato be monitored, that two units, which respectively comprise anobjective and a reflector, are arranged at diagonally opposite cornersof the area to be monitored, that the units are so rotatably arrangedthat one objective in each case scans the pattern field arrangedopposite to it, and that opposite each reflector a sensor means isplaced, onto which the objectives throw the image of the pattern field,and which scans the image and feeds corresponding signals to a signalprocessing means, which ascertains whether the image received by thesensor means possesses the same optical characteristics as the patternfields. In this respect, although two sensor means are required, a wholeseries of optical components is rendered unnecessary.

According to an advantageous development of the invention the sensormeans is a CCD camera as is presently commercially available at amoderate price. Such a camera can be operated in a simple manner as wellso that it supplies the necessary signals for the signal processingmeans.

A further advantageous feature of the invention is that the opticalcharacteristics of the pattern field are such that the pattern field isdivided up into light and dark area parts in a predetermined manner. Inthe case of such a pattern field it is possible to employ both thelightness or, respectively, color of the area parts and also thecontrast between the light and dark area parts for processing.

It is an advantage for the light area parts to have an orange color(marker color) and more particularly have a fluorescent coloringmaterial, because this renders it more readily possible to identify thelight areas.

A further advantageous development of the invention is such that thelight areas and the dark areas have complementary colors, as forinstance yellow and green, this meaning that a particularly simple wayof processing is created.

In the simplest case the pattern field is so structured that four areaparts are provided, diagonally oppositely placed area parts being lightand the two other area parts being dark.

In the monitoring system it is an advantage for the pattern fields to beprovided in the form of strips, which may be applied simply at therequired positions.

As an objective it is advantageously possible to utilize a convex lensand a collimator in order to produce a sufficiently sharp image of thepattern field on the sensor means.

In order to improve the image of the pattern field on the sensor meansthe objective or at least the convex lens is arranged in a slidingfashion for motion along the optic axis so that exact focussing ispossible.

In order to prevent external effects to the maximum extent the detectoris characterized in that at the objective a diaphragm is provided whichblanks out the image, which is thrown on the sensor means, with theexception of the image of the area parts.

It is furthermore an advantage if each reflector is set at 45° to theoptic axis of the associated objective so that on the image projectionsurface only an image of the pattern fields, and no other image, isproduced.

The reflectors are in this respect preferably arranged with an offset,equal to a step corresponding to the pattern field of one detector, in adownward direction and toward the objective. This means that the imagesof the individual pattern fields fit together in the image projectionarea without any gaps.

In accordance with an advantageous development of the invention themeans is characterized in that the reflector is a semi-transparentmirror and that on a basic area, which as regards the semi-transparentmirror arrangement is opposite to the image projection area, a referenceimage related to the image is provided on the image projection area inorder to check correct functioning of the arrangement. The sensor means(a CCD camera), which scans the image on the image projection surface,"looks at" the reference area through the semi-transparent mirror sothat when the sensor means detects a change in the opticalcharacteristics of the image without the ray path of a detector beinginterrupted, it is possible to conclude that there is a fault in thefunction of the arrangement.

The reflectors may be provided in a particularly simple fashion if theyare produced by machining one side face of an acrylic polymer body,whose top face, which is perpendicular to the side face, constitutes theimage projection surface.

In the case of the last mentioned embodiment of the invention it is anadvantage if the units are only able to be turned to and fro to such anextent that the pattern fields only are scanned. Accordingly there is nogap in time between one monitoring detector and the next one.

On the other hand it may be advantageous if the units are able to beturned through complete revolutions, and in this case, when theobjective is turned away from a pattern field, a reference image isscanned for checking correct operation of the arrangement. As a resultalthough there is no gap between one monitoring detector and the nextone, on the other hand the function of the arrangement is continuouslychecked.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagrammatic representation of an optical detector;

FIG. 2 is a diagrammatic representation of a monitoring means, which inprinciple comprises optical detectors as in FIG. 1;

FIG. 3 is a detailed view of the arrangement in FIG. 2;

FIG. 4 shows a monitoring means in accordance with a modified form ofthe invention; and

FIG. 5 is a diagrammatic representation of the optical means and of thesensor means in the embodiment of the invention of FIG. 4.

DESCRIPTION OF THE SPECIFIC EMBODIMENTS

FIG. 1 shows an optical detector 2, which possesses a pattern field 4 atthe end of a monitored area B. An objective 6 at the other end of themonitored area throws an image of the pattern field 4 on a sensor means8, which is more particularly a CCD camera. A signal processing means 10is connected with the CCD camera 8 in order to ascertain whether theimage received by the CCD camera 8 possesses the same opticalcharacteristics as the pattern field 4. For this purpose a referencepattern field with the same characteristics as those of the actualpattern field can be stored in the monitoring means 10.

The optical characteristics of the pattern field 4 are such that thepattern field 4 is divided in a predetermined fashion into light anddark area parts 12 and 14, four area parts being provided, of which twodiagonally opposite area parts are light and the two others are dark.The light area parts may have an orange color or possess a fluorescentcoloring material, whereas the dark area parts may be black. The lightarea parts 12 and the dark area parts 14 may also have complementarycolors, as for instance yellow and green.

The objective 6 may comprise a convex lens and a collimator in order toensure an exact imaging of the pattern field 4 on the sensor means 8.Furthermore the objective 6 or at least the convex lens may be arrangedfor sliding motion along the optic axis. For the objective 6 a diaphragm(not illustrated) may be provided which blanks out the image projectedby the objective 6 on the sensor means 8 with the exception of the imageof the area parts to avoid interfering effects.

The detector functions as follows. When an object intrudes into themonitored area, such object will as a rule possess a different degree ofbrightness or color to the light area part and/or dark area part of thepattern field. The camera detects the difference in lightness or incolor and the signal processing means will for example turn off themachien being monitored. A pattern field with light and dark area partswill ensure that even if the object intruding into the monitored areapossesses the same color or brightness (lightness) as for example thelight area part, the intrusion of such object will nevertheless bedetected, because the object will then also cover the dark area part sothat the detected optical characteristics will differ from those of thepattern field. It is in this manner that a reaction of the detector willbe ensured on every intrusion by an object.

Using such a detector monitoring means may be produced, with whichlarger areas may be monitored, two or more such optical detectors beingemployed and the processing of signals from a plurality of detectorsbeing performed in one or in two signal processing means.

FIG. 2 diagrammatically shows a monitoring means 20, which in principleis composed of optical detectors of the type described above, thedetectors being superposed. For example the pattern field 41 of the topdetector is illustrated together with the objective 6 comprising thelens 22 and the collimator 24. The lens is able to be slid in relationto the collimator along the optic axis in order to produce a sharp imageof the pattern field. Behind the objective 6 reflectors 26₁ through26_(n) are provided, which deflect the image rays from the objectiveonto an image surface 28, where they are scanned or sensed by the sensormeans, which supplies corresponding signals to the signal processingmeans (not illustrated).

Each of the reflectors 26₁ through 26_(n) is set at 45° to the opticaxis of the associated objective and the reflectors are arranged with anoffset, equal to a step corresponding to the pattern field of onedetector, in a downward direction and toward the objective as shown inFIG. 2. The result of this is an image free of gaps of the patternfields 4₁ through 4_(n) on the image surface 28.

As shown in FIG. 3 the reflectors are positioned on a side face 30 of anacrylic polymer body 32, whose end face constitutes the image surface213. The reflectors may be produced by coating or deposition from vaporon the surfaces of the acrylic polymer body 32.

As shown in FIG. 2, the acrylic polymer body 32 has an associated secondacrylic polymer body 34, on whose bottom surface a reference image 36 isprovided related to the image on the image surface 28. In FIG. 2 thereference image 36 is illustrated separate from the bottom surface ofthe acrylic polymer body 34 for the sake of simplification, thereference image 36 being provided on the bottom side of the acrylicpolymer body 34 in practice.

The reflectors 26 are in this embodiment of the invention in the form ofsemi-transparent mirrors so that the sensor means, which is opposite tothe image surface 28, "sees" both the image of the pattern fields andalso the reference surface 36 and the reference surface 36 may beincluded in processing and may be employed more particularly forchecking proper operation of the arrangement.

FIG. 4 diagrammatically shows another embodiment of a monitoring means40 composed of optical detectors of the type described above. In thecase of the monitoring means 40 a series of pattern fields 42 and 44 isarranged on the sides of a monitored area C. Two units 46 and 48, whichrespectively have an objective 50 and a reflector 52 (FIG. 5), arearranged at the diagonally opposite corners of the monitored area C. Theunits 46 and 48 are arranged rotatably so that the opposite patternfields 42 and, respectively, 48 may be scanned. The axis of rotation isin this case perpendicular in the plane of FIG. 5.

As shown in FIG. 5 the ray path from the objective 50 is via thereflector 52 to a filter 54 which for example is provided for an orangecolor, to a receiver 56, which accordingly responds to the fields withthe corresponding color. A further receiver 58 responds to the otherside of the pattern field 4 (FIG. 1) so that the two receivers haveoutputs in the form of signals with a 90° phase shift, if a patternfield in accordance with FIG. 1 is employed. If a plurality ofstrip-like pattern fields as in FIG. 1 are put together a stripedpattern field as in FIG. 1 will be produced consisting of individualpattern fields.

It is possible for the units 46 and 48 to be only rotatable to theextent that the pattern fields are scanned in sequence firstly in onedirection and then in the other direction, which are opposite to thatunit. As an alternative the units 46 and 48 may be arranged to berotatable through full turns. When during such a turn the objective 50is facing away from the pattern field, it will respond to a referencefield, which is provided at a suitable position on the rear side of theunit 46 and, respectively, 48 in order to check the proper function ofthe arrangement. It will be apparent that in this arrangement the unit46 monitors the area C₁ and the unit 48 the area C₂ and thatsimultaneously the operability of both units is monitored.

It is to be understood that the above description is intended to beillustrative and not restrictive. Many embodiments will be apparent tothose skilled in the art upon reviewing the above description. The scopeof the invention should, therefore, be determined not as reference tothe above description, but should instead be determined with referenceto the apended claims along with the full scope of equivalence to whichsuch claims are entitled.

What is claimed is:
 1. A monitoring means made up of optical detectors,comprisinga plurality of pattern fields, which are arranged at one endof the area to be monitored, objectives at the other end of the area tobe monitored and which are respectively associated with the patternfields, reflectors which deflect the image rays from the objectives ontoa image projection surface, a sensor means, onto which the objectivesthrow an image of the pattern field, and which scans the image andproduces scanning signals, and a processing means which is fed byscanning signals of the sensor means and which processing means isconfigured to ascertain whether the image received by the sensor meanspossesses the same optical characteristics as the pattern fields.
 2. Themonitoring means as claimed in claim 1, wherein the sensor means is aCCD camera.
 3. The monitoring means as claimed in claim 1, wherein theoptical characteristics of the pattern field are such that the patternfield is divided in a predetermined manner into light and dark areaparts.
 4. The monitoring means as claimed in claim 3, wherein the lightarea parts possesses an orange color.
 5. The monitoring means as claimedin claim 3, wherein the light area parts possesses a fluorescentcoloring material.
 6. The monitoring means as claimed in claim 3,wherein the light area parts and the dark area parts possessescomplementary colors as for example yellow and green.
 7. The monitoringmeans as claimed in claim 3, wherein four area parts are provided, twodiagonally opposite area partsbeing light and the two other ones beingdark.
 8. The monitoring means as claimed in claim 3, wherein the patternfields are provided in the form of strips.
 9. The monitoring means asclaimed in claim 1, wherein the objective is provided with a diaphragm,which blanks out an image thrown by the objective on the sensor meanswith the exception of the image of the area parts.
 10. The monitoringmeans as claimed in claim 1, wherein an objective is arranged forsliding motion along the optic axis.
 11. The monitoring means as claimedin claim 1, wherein an objective comprises a convex lens and acollimator.
 12. The monitoring means as claimed in claim 11, wherein theconvex lens is arranged for sliding motion along the optic axis.
 13. Themonitoring means as claimed in claim 1, wherein each reflector is at anangle of 45° to the optic axis of the associated objective.
 14. Themonitoring means as claimed in claim 13, wherein the reflectors arearranged with an offset, equal to a step corresponding to the patternfield of one detector, in a downward direction and toward the objective.15. A monitoring means made up of optical detectors whereina series ofpattern fields is arranged at opposite sides of an area to be monitored,two units, which respectively comprise an objective and a reflector, arearranged at diagonally opposite corners of the area to be monitored, theunits are so rotatably arranged that one objective in each case scansthe pattern field arranged opposite to it, and opposite each reflector asensor means is placed, onto which the objectives throw the image of thepattern field, and which scans the image and and produces scanningsignals, and a processing means which is fed by scanning signals of thesensor means and which processing means is configured to ascertainwhether the image received by the sensor means possesses the sameoptical characteristics as the pattern fields.
 16. The monitoring meansas claimed in claim 15, wherein the sensor means is a CCD camera. 17.The monitoring means as claimed in claim 15, wherein the opticalcharacteristics of the pattern field are such that the pattern field isdivided in a predetermined manner into light and dark area parts. 18.The monitoring means as claimed in claim 17, wherein the light areaparts possesses an orange color.
 19. The monitoring means as claimed inclaim 17, wherein the light area parts possesses a fluorescent coloringmaterial.
 20. The monitoring means as claimed in claim 17, wherein thelight area parts and the dark area parts possesses complementary colorsas for example yellow and green.
 21. The monitoring means as claimed inclaim 17, wherein four area parts are provided, two diagonally oppositearea partsbeing light and the two other ones being dark.
 22. Themonitoring means as claimed in claim 17, wherein the pattern fields areprovided in the form of strips.
 23. The monitoring means as claimed inclaim 15, wherein the objective is provided with a diaphragm, whichblanks out an image thrown by the objective on the sensor means with theexception of the image of the area parts.
 24. The monitoring means asclaimed in claim 15, wherein an objective is arranged for sliding motionalong the optic axis.
 25. The monitoring means as claimed in claim 15,wherein an objective comprises a convex lens and a collimator.
 26. Themonitoring means as claimed in claim 25, wherein the convex lens isarranged for sliding motion along the optic axis.
 27. The monitoringmeans as claimed in claim 15, wherein each reflector is at an angle of45° to the optic axis of the associated objective.
 28. The monitoringmeans as claimed in claim 15, wherein the reflectors are arranged withan offset, equal to a step corresponding to the pattern field of onedetector, in a downward direction and toward the objective.
 29. Themonitoring means as claimed in claim 15, wherein the reflector is asemi-transparent mirror and in that on a basic area, which as regards,the semi-transparent mirror arrangement is opposite to the imageprojection area, a reference image related to the image is provided onthe image projection area is produced.
 30. The monitoring means asclaimed in claim 15, wherein the reflectors are produced by machiningone side face of an acrylic polymer body, whose top face, which isperpendicular to the side face, constitutes the image projection area.31. The monitoring means as claimed in claims 15, wherein the units areonly able to be turned to such an extent that the pattern fields onlyare scanned.
 32. The monitoring means as claimed in claim 15, whereinthe units are able to be turned through complete revolutions, and inthis case, when the objective is turned away from a pattern field, areference image is detected for checking correct operation of thearrangement.